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Session: Neurophysiology & Sleep
Session starts: Thursday 26 January, 10:30
Presentation starts: 10:30
Room: Room 530

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Fokke van Meulen (Center for Sleep Medicine Kempenhaeghe, The Netherlands)
Juha Kortelainen (VTT, Finland)
Mervi Hirvonen (VTT, Finland)
Hans van Dijk (Center for Sleep Medicine Kempenhaeghe, The Netherlands)
Johan Plomp (VTT, Finland)
Sebastiaan Overeem (Center for Sleep Medicine Kempenhaeghe, The Netherlands)

Abstract:
Polysomnography (PSG) is widely used in clinical practice as the gold standard in monitoring sleep, but the large amount of wired sensors may influence actual sleep quality and a less representative assessment of sleep as a result. We aim to develop a radar-based method for the unobtrusive assessment of vital signs parameters that are part of the current PSG setup. A 60 GHz Frequency-Modulated Continuous Wave radar system (VTT, Finland) was installed above the head side of a bed in the clinical sleep laboratory of Sleep Medicine Center Kempenhaeghe (Heeze, Netherlands). The radar operates with multiple transmit and receiving antennas to construct a two-dimensional image. The measured signals show micro vibrations at the skin surface with 110 Hz sampling rate. Combined with advanced data processing techniques it allows the detection of heart beats and respiratory movements. Simultaneously recording PSG and radar data allows the validation of vital signs parameters estimated by radar against their gold-standard counterparts. Recruited patients had a variety of (suspected) sleep disorders and were scheduled for a video-polysomnography as part of their diagnostic trajectory. Between September 2021 and February 2022, 43 participants were included in the study. Using the radar-based setup it was possible to detect heart rate with a mean average error of 2.4 beats per minute compared to ECG. The respiration rate shows a mean average error of 0.58 breaths per minute compared to the RIP belts signal. On average the coverage was 98.5% of the nocturnal recording. After reviewing the data, general causes for error were cardiac arrhythmias and motion artefacts. The radar-based setup allows the measurement of heart rate and respiration rate in an accurate and completely unobtrusive manner. In future, surrogate measures for sleep architecture will be obtained, as well as pathological events, such as sleep related breathing and movement events. In contrast with other radar based vital signs monitoring approaches, our setup allows the detection of movements in a two-dimensional plane, and therefore has the potential of detecting larger body movements, such as limb movements and sleeping posture, as well as the ability to separately monitor vital signs of bed partners.